[ben_w]

Just to add, by definition 6σ is one in a billion. It isn’t just “profoundly gifted”, but rather “there are seven of you”.

[barry-cotter]

IQ is a fat tailed distribution. There are way more people in the tails than the test’s definition and morning would suggest.

[ben_w]

IQ is defined to be a normal distribution. Intelligence, on the other hand, isn’t.

This is one of the problems with IQ as a measure of intelligence. IQ 150 doesn’t mean doing mental arithmetic faster than IQ 100 by the same margin that IQ 100 beats IQ 50, only that IQ>150 is as rare as IQ<50.